Trendspotting: Age of Puberty Keeps Falling

NewsWire: 6/6/22

• Children, especially girls, are entering puberty at ever-earlier ages. This phenomenon, which has puzzled doctors for years, has sped up during the pandemic. (The New York Times)
• NH: Studies show that puberty is starting earlier and earlier for girls. This shift has drawn renewed attention during the pandemic, with doctors around the world noting an unusual surge in cases of early puberty. Girls who go through puberty earlier are at a higher risk for depression, anxiety, substance abuse, and other psychological issues--and in adulthood, breast and uterine cancer.
• The big question: Why is this happening?
• Researchers first took note of this phenomenon 25 years ago. In 1997, an American physician assistant named Marcia Herman-Giddens published a landmark study of more than 17,000 girls showing that, on average, puberty was beginning earlier than it used to. On average, girls were beginning to develop breasts--typically the first sign of puberty--around age 10, or more than a year earlier than previously recorded. Among black girls, this was happening even earlier at age 9.
• In the decades since, study after study has confirmed these findings. One published in JAMA Pediatrics last April concluded that, across two dozen countries, the age of puberty in girls has fallen by an average of three months per decade since the 1970s. Currently, the earliest age of onset is in the U.S. (age range: 8.8 to 10.3 years). The age of puberty has also been falling for boys, but the decline has been less extreme.
• As children hit puberty at younger ages, pediatricians are also seeing more cases of “precocious puberty”: puberty that begins before age 8 for girls and 9 for boys. During the pandemic, the number of these cases has spiked. A 2021 study conducted in Italy, which examined five pediatric clinics around the country, reported that 328 girls were referred for early puberty between March and September 2020. That’s more than twice as many as the 140 who were referred over the same period in 2019. Doctors have also reported seeing more precocious puberty cases in Turkey, India, and the U.S.
• By itself, the earlier onset of puberty is not necessarily a marker of ill health. Over the century leading up to 1970, it was a sign that living standards were improving: better nutrition, less air pollution, fewer fatal infectious diseases, and the like. In 1840, girls in Western countries got their first period at an average age of 16.5. (Even today, it’s well-known that hard athletic training for girls--think gymnasts or long-distance runners with low body-fat ratios--can delay their age of puberty well into their teens or even 20s.) Since 1970, however, doctors and researchers fear that more harmful forces are behind the shift, including obesity, stress, and the presence of endocrine-disrupting chemicals (EDCs) in the environment.
• Girls who go through puberty earlier are also more likely to develop depression, anxiety, and other psychological issues in adolescence than those who experience it later. And in adulthood, they’re at a higher risk of developing breast or uterine cancer and experiencing early menopause.
• Obesity is the best-established of the factors thought to be driving the age decline. Numerous studies dating back to the 1970s have linked obesity with earlier puberty for both girls and boys. Stress is another trigger, with researchers linking earlier puberty to everything from unstable family relationships to growing up in poverty. Both obesity rates and stress increased sharply during the pandemic (see “New Evidence of Surge in Childhood Obesity”), which might explain the increased incidence of early puberty cases.
• The other major suspect is EDCs, which we discussed at length in last year’s piece about the physiological factors behind declining fertility. (See “Coming Soon…Children of Men?”) Just as EDCs may be wreaking havoc on adults’ reproductive health, they also may be triggering, through some parallel biological gateway, earlier puberty. These chemicals include phthalates, which are often used in the production of plastics, and bisphenols (including BPA), which are typically found in hard plastics like water bottles and food storage containers. There’s growing evidence that exposure to EDCs is in itself associated with a higher risk of obesity and Type 2 diabetes. If this turns out to be true, it would constitute a further positive feedback loop.
• One might ask if earlier puberty onset should really be considered a public health problem. If the average is moving downwards, should we just accept it as the new normal? The standards for what are considered the normal ages of puberty were established in the 1960s, and some experts argue that they’re just out of date.
• IMO, the answer is clearly no. Although you might say that the age of puberty in itself doesn't seem terribly consequential, it’s associated with drivers that are all correlated with poorer health, both physically and emotionally--and both in the present and over the long term. We need to care about this for the same reasons that we care about reducing rates of childhood obesity. If kids were maturing earlier for positive reasons, then that might be considered progress. But that's not the case here.